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Crust Archaean

Bowring S. A., King J. E., Housh T. B., Isachsen C. E., and Podosek E. A. (1989b) Neodymium and lead isotope evidence for enriched early Archaean crust in North America. Nature 340, 222—225. [Pg.1603]

Kroner A., Compston W., and WiUiams 1. S. (1989) Growth of early Archaean crust in the Ancient Gneiss Complex of Swaziland as revealed by single zircon dating. Tectonophy-sics 161, 271-298. [Pg.1606]

Archaean cratons have long been prime targets for a broad array of scientific studies, partly because they form the oldest cores of the continents, but also because they have economic significance as a major source of the world s mineral wealth. (The term craton is confined here to Archaean crust, although the word is commonly applied to Proterozoic shields as well. The Archaean-Proterozoic boundary is, as always, imprecisely defined, but in southern Africa is marked by a sufficient hiatus in time that there is no difficulty... [Pg.1]

The Vredefort structure a cross-section of Archaean crust... [Pg.5]

There are, however, interesting details that are to date unique to the Western Superior Provinee. These include thicker than normal Archaean crust, a slab-like velocity anomaly in the mantle transition zone, and large SKS splitting in the Archaean Superior Province but little spUtting in the surrounding Trans-Hudson Proterozoic shear zone. [Pg.27]

Davis, W. J., Gariepy, C. van Breemen, O. 1996. Pb isotopic composition of late Archaean granites and the extent of recycling early Archaean crust in the Slave Province, northwest Canada. Chemical Geology, 130, 244-269. [Pg.120]

Yamashita, K., Greaser, R. A., Jensen, J. E. Heaman, L. M. 2000. Origin and evolution of mid- to late-Archaean crust in the Hanikahimajuk Lake Area, Slave province, Canada evidence from U-Pb geochronological, geochemical and Nd-Pb isotopic data. Precambrian Research, 99, 197-224. [Pg.124]

First of all, Archaean crust occupies a mere 7-11 miUionkm (c. 5-7.5% Goodwin 1996 de... [Pg.151]

It is critical therefore that we go back to the primary rock record and look for signals of processes other than those that may have had their origin in modern-style plate tectonics. In this context I will discuss some important themes in Archaean geology and highlight those features that perhaps appear uniquely Archaean. As part of this discussion I will present new data from the Slave craton, including the first craton-scale cross-section through this well-exposed fragment of Archaean crust. [Pg.153]

Widespread stabilization oI Archaean crust, typically after terminal granite bloom (e.g. 2.60-2,58 Ga granites of Slave craton) 2.65-2.55 Ga e.g. Davis Bleeker 1999... [Pg.155]

Collins, W. J., van Kranendonk, M. J. Teyssier, C. 1998. Partial convective overturn of Archaean crust in the East Pilbara Craton, Western Austra-... [Pg.175]

Goodwin, A. M. Smith, J. E. M. 1980. Chemical discontinuities in Archaean volcanic terrain and the development of Archaean crust. Precambrian Research, 10, 301-311. [Pg.209]

Ludden, j., Hubert, C., Barnes, C., Milkereit, B. Sawyer, E. 1993. A three dimensional perspective on the evolution of Archaean crust LITHO-PROBE seismic reflection images in the southwestern Superior province. Lithos, 30, 357-372. [Pg.210]

Of these, late Archaean sedimentary basins are the most "modern" in their form and can be clearly recognized as upper crust. Similarly, the relatively low metamorphic grade of many Archaean greenstone belts indicates that they too represent upper Archaean crust. In contrast, Archaean granite-gneiss terrains more commonly belong to the deeper continental crust and variously represent middle to lower continental crust. There are only a few places... [Pg.10]

Current models of Archaean crust generation imply that subduction is a relatively ancient process operating since at least about 3.5 Ga. An outstanding question is the relative contribution that plume magmatism has made to the generation of felsic continental crust. [Pg.133]

Archaean crust-forming processes play a pivotal role in shaping the structure of the Earth s continental crust,. .. so that... we need to increasingly focus our attention on the distant past, as the key to understanding the present (Kemp Si Hawkesworth, 2003)... [Pg.134]

FIGURE 4.6 A plot of eNd versus time for samples of Proterozoic crust from North America and Europe (grey boxes). The age of the samples was fixed from their U-Pb zircon age. The Nd-isotope compositions are interpreted as mixing between a depleted mantle source, indicative of juvenile crust, and recycled Archaean crust. The % curves indicate the proportion of reworked Archaean crust incorporated into Proterozoic crust and hence the proportion of truly juvenile crust formed (data from Patchett Arndt, 1986) after Rollinson (2006). [Pg.144]

A potentially significant reservoir, and one which a number of authors have suggested is important in the context of continent formation, is the subcontinental lithospheric mantle (SCLM). Kramers (1987, 1988), suggested that the TTG magmas of the Archaean crust formed in an open-system magma layer in the early Earth, the cumulates from which are now preserved as the SCLM. More recently Abbott et al. (2000) proposed a model of continental growth founded upon the premise that the continental crust was extracted from the SCLM. [Pg.166]

Table 4.3 below summarizes the different reservoirs thought to be present in the modern silicate Earth. However, of these, only the depleted mantle and buried eclogitic slabs have compositions which make them directly complementary to the composition of the continental crust. It is suggested here that Archaean SCLM is not closely related in a geochemical sense to Archaean felsic crust but is the product of basalt extraction, basalt which now is emplaced within the Archaean crust. In contrast, Phanerozoic SCLM may be the restite-complement of the basaltic precursor to modern crust. The proposal that there was an early-formed (pre 3.7 Ga), enriched, basaltic crust (Section 4.5.1.2.2), if confirmed, has important implications for the balance between the major Earth reservoirs, not least because the primitive mantle and the bulk silicate Earth can no longer be regarded as com-positionally identical. [Pg.168]


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Archaean

Archaean crust thickness

Continental crust Archaean

Oceanic crust thickness, Archaean

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